Re: [PATCH Part2 v5 23/45] KVM: SVM: Add KVM_SNP_INIT command

From: Marc Orr
Date: Thu Sep 09 2021 - 23:32:29 EST

On Fri, Aug 20, 2021 at 9:00 AM Brijesh Singh <brijesh.singh@xxxxxxx> wrote:
>
> The KVM_SNP_INIT command is used by the hypervisor to initialize the
> SEV-SNP platform context. In a typical workflow, this command should be the
> first command issued. When creating SEV-SNP guest, the VMM must use this
> command instead of the KVM_SEV_INIT or KVM_SEV_ES_INIT.
>
> The flags value must be zero, it will be extended in future SNP support to
> communicate the optional features (such as restricted INT injection etc).
>
> Co-developed-by: Pavan Kumar Paluri <papaluri@xxxxxxx>
> Signed-off-by: Pavan Kumar Paluri <papaluri@xxxxxxx>
> Signed-off-by: Brijesh Singh <brijesh.singh@xxxxxxx>
> ---
> .../virt/kvm/amd-memory-encryption.rst | 27 ++++++++++++
> arch/x86/include/asm/svm.h | 2 +
> arch/x86/kvm/svm/sev.c | 44 ++++++++++++++++++-
> arch/x86/kvm/svm/svm.h | 4 ++
> include/uapi/linux/kvm.h | 13 ++++++
> 5 files changed, 88 insertions(+), 2 deletions(-)
>
> diff --git a/Documentation/virt/kvm/amd-memory-encryption.rst b/Documentation/virt/kvm/amd-memory-encryption.rst
> index 5c081c8c7164..7b1d32fb99a8 100644
> --- a/Documentation/virt/kvm/amd-memory-encryption.rst
> +++ b/Documentation/virt/kvm/amd-memory-encryption.rst
> @@ -427,6 +427,33 @@ issued by the hypervisor to make the guest ready for execution.
>
> Returns: 0 on success, -negative on error
>
> +18. KVM_SNP_INIT
> +----------------
> +
> +The KVM_SNP_INIT command can be used by the hypervisor to initialize SEV-SNP
> +context. In a typical workflow, this command should be the first command issued.
> +
> +Parameters (in/out): struct kvm_snp_init
> +
> +Returns: 0 on success, -negative on error
> +
> +::
> +
> + struct kvm_snp_init {
> + __u64 flags;
> + };
> +
> +The flags bitmap is defined as::
> +
> + /* enable the restricted injection */
> + #define KVM_SEV_SNP_RESTRICTED_INJET (1<<0)
> +
> + /* enable the restricted injection timer */
> + #define KVM_SEV_SNP_RESTRICTED_TIMER_INJET (1<<1)
> +
> +If the specified flags is not supported then return -EOPNOTSUPP, and the supported
> +flags are returned.
> +
> References
> ==========
>
> diff --git a/arch/x86/include/asm/svm.h b/arch/x86/include/asm/svm.h
> index 44a3f920f886..a39e31845a33 100644
> --- a/arch/x86/include/asm/svm.h
> +++ b/arch/x86/include/asm/svm.h
> @@ -218,6 +218,8 @@ struct __attribute__ ((__packed__)) vmcb_control_area {
> #define SVM_NESTED_CTL_SEV_ENABLE BIT(1)
> #define SVM_NESTED_CTL_SEV_ES_ENABLE BIT(2)
>
> +#define SVM_SEV_FEAT_SNP_ACTIVE BIT(0)
> +
> struct vmcb_seg {
> u16 selector;
> u16 attrib;
> diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
> index 50fddbe56981..93da463545ef 100644
> --- a/arch/x86/kvm/svm/sev.c
> +++ b/arch/x86/kvm/svm/sev.c
> @@ -235,10 +235,30 @@ static void sev_unbind_asid(struct kvm *kvm, unsigned int handle)
> sev_decommission(handle);
> }
>
> +static int verify_snp_init_flags(struct kvm *kvm, struct kvm_sev_cmd *argp)
> +{
> + struct kvm_snp_init params;
> + int ret = 0;
> +
> + if (copy_from_user(&params, (void __user *)(uintptr_t)argp->data, sizeof(params)))
> + return -EFAULT;
> +
> + if (params.flags & ~SEV_SNP_SUPPORTED_FLAGS)
> + ret = -EOPNOTSUPP;
> +
> + params.flags = SEV_SNP_SUPPORTED_FLAGS;
> +
> + if (copy_to_user((void __user *)(uintptr_t)argp->data, &params, sizeof(params)))
> + ret = -EFAULT;
> +
> + return ret;
> +}
> +
> static int sev_guest_init(struct kvm *kvm, struct kvm_sev_cmd *argp)
> {
> + bool es_active = (argp->id == KVM_SEV_ES_INIT || argp->id == KVM_SEV_SNP_INIT);
> struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
> - bool es_active = argp->id == KVM_SEV_ES_INIT;
> + bool snp_active = argp->id == KVM_SEV_SNP_INIT;
> int asid, ret;
>
> if (kvm->created_vcpus)
> @@ -249,12 +269,22 @@ static int sev_guest_init(struct kvm *kvm, struct kvm_sev_cmd *argp)
> return ret;
>
> sev->es_active = es_active;
> + sev->snp_active = snp_active;
> asid = sev_asid_new(sev);
> if (asid < 0)
> goto e_no_asid;
> sev->asid = asid;
>
> - ret = sev_platform_init(&argp->error);
> + if (snp_active) {
> + ret = verify_snp_init_flags(kvm, argp);
> + if (ret)
> + goto e_free;
> +
> + ret = sev_snp_init(&argp->error);
> + } else {
> + ret = sev_platform_init(&argp->error);
> + }
> +
> if (ret)
> goto e_free;
>
> @@ -600,6 +630,10 @@ static int sev_es_sync_vmsa(struct vcpu_svm *svm)
> save->pkru = svm->vcpu.arch.pkru;
> save->xss = svm->vcpu.arch.ia32_xss;
>
> + /* Enable the SEV-SNP feature */
> + if (sev_snp_guest(svm->vcpu.kvm))
> + save->sev_features |= SVM_SEV_FEAT_SNP_ACTIVE;
> +
> return 0;
> }
>
> @@ -1532,6 +1566,12 @@ int svm_mem_enc_op(struct kvm *kvm, void __user *argp)
> }
>
> switch (sev_cmd.id) {
> + case KVM_SEV_SNP_INIT:
> + if (!sev_snp_enabled) {
> + r = -ENOTTY;
> + goto out;
> + }
> + fallthrough;
> case KVM_SEV_ES_INIT:
> if (!sev_es_enabled) {
> r = -ENOTTY;
> diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
> index 01953522097d..57c3c404b0b3 100644
> --- a/arch/x86/kvm/svm/svm.h
> +++ b/arch/x86/kvm/svm/svm.h
> @@ -69,6 +69,9 @@ enum {
> /* TPR and CR2 are always written before VMRUN */
> #define VMCB_ALWAYS_DIRTY_MASK ((1U << VMCB_INTR) | (1U << VMCB_CR2))
>
> +/* Supported init feature flags */
> +#define SEV_SNP_SUPPORTED_FLAGS 0x0
> +
> struct kvm_sev_info {
> bool active; /* SEV enabled guest */
> bool es_active; /* SEV-ES enabled guest */
> @@ -81,6 +84,7 @@ struct kvm_sev_info {
> u64 ap_jump_table; /* SEV-ES AP Jump Table address */
> struct kvm *enc_context_owner; /* Owner of copied encryption context */
> struct misc_cg *misc_cg; /* For misc cgroup accounting */
> + u64 snp_init_flags;

This field never gets set anywhere. Should it get set in
`verify_snp_init_flags()`?

> };
>
> struct kvm_svm {
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index d9e4aabcb31a..944e2bf601fe 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -1712,6 +1712,9 @@ enum sev_cmd_id {
> /* Guest Migration Extension */
> KVM_SEV_SEND_CANCEL,
>
> + /* SNP specific commands */
> + KVM_SEV_SNP_INIT,
> +
> KVM_SEV_NR_MAX,
> };
>
> @@ -1808,6 +1811,16 @@ struct kvm_sev_receive_update_data {
> __u32 trans_len;
> };
>
> +/* enable the restricted injection */
> +#define KVM_SEV_SNP_RESTRICTED_INJET (1 << 0)
> +
> +/* enable the restricted injection timer */
> +#define KVM_SEV_SNP_RESTRICTED_TIMER_INJET (1 << 1)
> +
> +struct kvm_snp_init {
> + __u64 flags;
> +};
> +
> #define KVM_DEV_ASSIGN_ENABLE_IOMMU (1 << 0)
> #define KVM_DEV_ASSIGN_PCI_2_3 (1 << 1)
> #define KVM_DEV_ASSIGN_MASK_INTX (1 << 2)
> --
> 2.17.1
>
>